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The regulation of mitochondrial DNA copy number in glioblastoma cells.

Dickinson A, Yeung KY, Donoghue J, Baker MJ, Kelly RD, McKenzie M, Johns TG, St John JC - Cell Death Differ. (2013)

Bottom Line: As stem cells undergo differentiation, mitochondrial DNA (mtDNA) copy number is strictly regulated in order that specialized cells can generate appropriate levels of adenosine triphosphate (ATP) through oxidative phosphorylation (OXPHOS) to undertake their specific functions.We show that human neural stem cells (hNSCs) increased their mtDNA content during differentiation in a process that was mediated by a synergistic relationship between the nuclear and mitochondrial genomes and results in increased respiratory capacity.However, prolonged depletion resulted in impaired mtDNA replication, reduced proliferation and induced the expression of early developmental and pro-survival markers including POU class 5 homeobox 1 (OCT4) and sonic hedgehog (SHH).

View Article: PubMed Central - PubMed

Affiliation: 1] The Mitochondrial Genetics Group, Centre for Genetic Diseases, Monash Institute of Medical Research, Monash University, 27-31 Wright Street, Clayton, Victoria 3168, Australia [2] Molecular Basis of Metabolic Disease, Division of Metabolic and Vascular Health, Warwick Medical School, The University of Warwick, Clifford Bridge Road, Coventry, CV2 2DX, UK.

ABSTRACT
As stem cells undergo differentiation, mitochondrial DNA (mtDNA) copy number is strictly regulated in order that specialized cells can generate appropriate levels of adenosine triphosphate (ATP) through oxidative phosphorylation (OXPHOS) to undertake their specific functions. It is not understood whether tumor-initiating cells regulate their mtDNA in a similar manner or whether mtDNA is essential for tumorigenesis. We show that human neural stem cells (hNSCs) increased their mtDNA content during differentiation in a process that was mediated by a synergistic relationship between the nuclear and mitochondrial genomes and results in increased respiratory capacity. Differentiating multipotent glioblastoma cells failed to match the expansion in mtDNA copy number, patterns of gene expression and increased respiratory capacity observed in hNSCs. Partial depletion of glioblastoma cell mtDNA rescued mtDNA replication events and enhanced cell differentiation. However, prolonged depletion resulted in impaired mtDNA replication, reduced proliferation and induced the expression of early developmental and pro-survival markers including POU class 5 homeobox 1 (OCT4) and sonic hedgehog (SHH). The transfer of glioblastoma cells depleted to varying degrees of their mtDNA content into immunocompromised mice resulted in tumors requiring significantly longer to form compared with non-depleted cells. The number of tumors formed and the time to tumor formation was relative to the degree of mtDNA depletion. The tumors derived from mtDNA depleted glioblastoma cells recovered their mtDNA copy number as part of the tumor formation process. These outcomes demonstrate the importance of mtDNA to the initiation and maintenance of tumorigenesis in glioblastoma multiforme.

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Related in: MedlinePlus

Gene expression analysis of markers of pluripotency and self-renewal in undifferentiated and mtDNA depleted GBM cells. Gene expression for undifferentiated and mtDNA depleted HSR-GBM1 cells was determined relative to β-ACTIN and as fold changes relative to non-depleted cells for OCT4 (a), NANOG (b), SOX2 (c), c-MYC (d) and hTERT (e). Bars represent mean values±S.E.M. *P<0.05, **P<0.01 and ***P<0.001
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fig3: Gene expression analysis of markers of pluripotency and self-renewal in undifferentiated and mtDNA depleted GBM cells. Gene expression for undifferentiated and mtDNA depleted HSR-GBM1 cells was determined relative to β-ACTIN and as fold changes relative to non-depleted cells for OCT4 (a), NANOG (b), SOX2 (c), c-MYC (d) and hTERT (e). Bars represent mean values±S.E.M. *P<0.05, **P<0.01 and ***P<0.001

Mentions: As there were significant increases in expression of early developmental markers, we analyzed POU class 5 homeobox 1 (OCT4), Nanog homeobox (NANOG), sex determining region Y-box 2 (SOX2), V-Myc myelocytomatosis viral oncogene homolog (Avian) (c-MYC) and human telomerase reverse transcriptase (hTERT), which are associated with pluripotency, cell proliferation and self-renewal. Although the expression of OCT4 (Figure 3a), NANOG (Figure 3b), SOX2 (Figure 3c), c-MYC (Figure 3d) and hTERT (Figure 3e) fluctuated over the first 25 days of mtDNA depletion, only OCT4 expression increased (threefold) by day 50 (P<0.001).


The regulation of mitochondrial DNA copy number in glioblastoma cells.

Dickinson A, Yeung KY, Donoghue J, Baker MJ, Kelly RD, McKenzie M, Johns TG, St John JC - Cell Death Differ. (2013)

Gene expression analysis of markers of pluripotency and self-renewal in undifferentiated and mtDNA depleted GBM cells. Gene expression for undifferentiated and mtDNA depleted HSR-GBM1 cells was determined relative to β-ACTIN and as fold changes relative to non-depleted cells for OCT4 (a), NANOG (b), SOX2 (c), c-MYC (d) and hTERT (e). Bars represent mean values±S.E.M. *P<0.05, **P<0.01 and ***P<0.001
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3824586&req=5

fig3: Gene expression analysis of markers of pluripotency and self-renewal in undifferentiated and mtDNA depleted GBM cells. Gene expression for undifferentiated and mtDNA depleted HSR-GBM1 cells was determined relative to β-ACTIN and as fold changes relative to non-depleted cells for OCT4 (a), NANOG (b), SOX2 (c), c-MYC (d) and hTERT (e). Bars represent mean values±S.E.M. *P<0.05, **P<0.01 and ***P<0.001
Mentions: As there were significant increases in expression of early developmental markers, we analyzed POU class 5 homeobox 1 (OCT4), Nanog homeobox (NANOG), sex determining region Y-box 2 (SOX2), V-Myc myelocytomatosis viral oncogene homolog (Avian) (c-MYC) and human telomerase reverse transcriptase (hTERT), which are associated with pluripotency, cell proliferation and self-renewal. Although the expression of OCT4 (Figure 3a), NANOG (Figure 3b), SOX2 (Figure 3c), c-MYC (Figure 3d) and hTERT (Figure 3e) fluctuated over the first 25 days of mtDNA depletion, only OCT4 expression increased (threefold) by day 50 (P<0.001).

Bottom Line: As stem cells undergo differentiation, mitochondrial DNA (mtDNA) copy number is strictly regulated in order that specialized cells can generate appropriate levels of adenosine triphosphate (ATP) through oxidative phosphorylation (OXPHOS) to undertake their specific functions.We show that human neural stem cells (hNSCs) increased their mtDNA content during differentiation in a process that was mediated by a synergistic relationship between the nuclear and mitochondrial genomes and results in increased respiratory capacity.However, prolonged depletion resulted in impaired mtDNA replication, reduced proliferation and induced the expression of early developmental and pro-survival markers including POU class 5 homeobox 1 (OCT4) and sonic hedgehog (SHH).

View Article: PubMed Central - PubMed

Affiliation: 1] The Mitochondrial Genetics Group, Centre for Genetic Diseases, Monash Institute of Medical Research, Monash University, 27-31 Wright Street, Clayton, Victoria 3168, Australia [2] Molecular Basis of Metabolic Disease, Division of Metabolic and Vascular Health, Warwick Medical School, The University of Warwick, Clifford Bridge Road, Coventry, CV2 2DX, UK.

ABSTRACT
As stem cells undergo differentiation, mitochondrial DNA (mtDNA) copy number is strictly regulated in order that specialized cells can generate appropriate levels of adenosine triphosphate (ATP) through oxidative phosphorylation (OXPHOS) to undertake their specific functions. It is not understood whether tumor-initiating cells regulate their mtDNA in a similar manner or whether mtDNA is essential for tumorigenesis. We show that human neural stem cells (hNSCs) increased their mtDNA content during differentiation in a process that was mediated by a synergistic relationship between the nuclear and mitochondrial genomes and results in increased respiratory capacity. Differentiating multipotent glioblastoma cells failed to match the expansion in mtDNA copy number, patterns of gene expression and increased respiratory capacity observed in hNSCs. Partial depletion of glioblastoma cell mtDNA rescued mtDNA replication events and enhanced cell differentiation. However, prolonged depletion resulted in impaired mtDNA replication, reduced proliferation and induced the expression of early developmental and pro-survival markers including POU class 5 homeobox 1 (OCT4) and sonic hedgehog (SHH). The transfer of glioblastoma cells depleted to varying degrees of their mtDNA content into immunocompromised mice resulted in tumors requiring significantly longer to form compared with non-depleted cells. The number of tumors formed and the time to tumor formation was relative to the degree of mtDNA depletion. The tumors derived from mtDNA depleted glioblastoma cells recovered their mtDNA copy number as part of the tumor formation process. These outcomes demonstrate the importance of mtDNA to the initiation and maintenance of tumorigenesis in glioblastoma multiforme.

Show MeSH
Related in: MedlinePlus